Field of the Invention
The present invention relates to a terminal for aluminum electric wire connection and a method for producing the same.
Description of Related Art
In recent years, there are increasing demands for an aluminum electric wire, which is light in weight and low in cost, for the purpose of achieving both an improvement of energy efficiency and a reduction of cost. In a case where this electric wire having the above characteristics is connected to an electric apparatus, means for connecting copper and aluminum is needed because a wire in the electric apparatus is copper in many cases, and a copper-alloy terminal is often used as such means. Various methods such as a method using soldering, a method using an ultrasonic wave, a method using fusing, and a method using laser have been proposed as a method for the terminal connection. Especially soldering is an excellent method that provides reliable joining because soldering makes it possible to firmly connect an entire connection part in a case where a large number of aluminum wires are connected.
However, in general, in a case where an aluminum electric wire is connected to a copper-alloy terminal, an aluminum wire in the terminal does not reach a predetermined necessary temperature due to low heat conductivity of the copper-alloy terminal even when the terminal is heated in soldering. It is therefore undesirably hard to introduce a flux or molten solder into the whole of the inside of the terminal. This results in formation of voids in the solder and parts that are not soldered, thereby causing a problem that the reliability of electrical joining becomes low. The voids can be a cause of discharge, occurrence of electric erosion, an increase of electric resistance, generation of heat during application of electricity, and the like and are therefore not desirable. Furthermore, the voids easily include air and moisture, and thermal conductivity decreases due to the presence of air and moisture. This leads to less certainty of joining. Meanwhile, in a case where the terminal and an end of the electric wire are compressed by swaging with great force in order to reduce voids and improve thermal conductivity, there is a risk of damaging of the electric wire and even breaking of the electric wire.
Techniques concerning joining between an electric wire and a terminal are, for example, disclosed in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a technique concerning a connection terminal for ultrasonic wave joining between an aluminum electric wire and a terminal made of copper using an ultrasonic horn chip, and Patent Document 2 discloses a technique concerning a terminal metal fitting including a pipe-like conductor connection part that is integral with a plate member main body made of aluminum and into which a twisted-wire conductor is inserted, and a dissimilar-metal layer that is made of a metal that is not aluminum and is provided on a bottom surface of the plate member main body.